The balancing of rotational components in various mechanical devices and systems has been a subject of investigation and development throughout modern industrial history. Where rotary components operate under conditions of balance falling within acceptable performance parameters, their efficiency and operational life spans are considerably improved. Thus, industry has recognized the cost justification of accepting machinery down time and labor cost penalties associated with the carrying out of rotor component balancing.
For example, large, material moving fans often find service within hostile, corrosive environments. They become unbalanced very often in consequence of the loss of pieces of blades. To maintain them in service, the fans are stripped down, rebalanced and returned to service. As a result, bearing damage or the like is essentially prevented and the life spans for the fans are extensible until such times as they are incapable of maintaining desired fluid flow.
A broad variety of rotor balancing techniques have been evolved by industry. An important one of these techniques look to a mathematically based evaluation of unbalance generated rotor vibration wherein product detection procedures are carried out to determine vector representation signals of unbalance. From these signals, the amount and position of correctional weight adjustment may be derived.
One category of balancing devices is concerned with "dedicated" balancing machines. These machines operate in conjunction with somewhat elaborate supports or pedestals having carefully predetermined geometries and rotor bearing characteristics upon which the rotor component desired to be balanced is mounted. Employing either displacement or thrust transducers at specific positions or "planes", as well as phase or rotational position monitors, the rotational manipulation of the rotor to be balanced in conjunction with calibration procedures produces vector categorized signals. These signals are operated upon by any of a broad variety of computational systems to generate appropriate balancing information.
Generally, the above-described dedicated balancing devices are installed in somewhat permanent or semi-permanent plant locations such that the rotational components of remote machinery installations must be removed and transported varying distances for access to the balancing services. Of course, such procedures involve the expense of rotor transportation and extended down times.
These expenses have led industry to resort to the use of less accurate but portable vibration analyzing instruments for providing balance correction at the situs of the equipment. The use of vibration analyzers for this purpose of balancing rotors generally has required that personnel in the field carry out a sequence of relatively extended procedures and mathematical computations. In consequence, a human error factor enters the procedure and the time heretofore required for carrying out such in situ balancing becomes somewhat extended. The vibration analyzers involved in this field procedure generally are tunable filters operating in conjuction with strobe lights and vibration transducers or pick-ups. With the procedure, the operator provides some form of reference mark which rotates with the rotor being balanced, applies the vibration transducers at locations adjacent the planes at which correction will be applied, and then carries out a sequence of analytical steps. These steps involve, for example, causing the rotor to operate at working speed and recording resultant vibration data; stopping the rotor and applying a trial weight at a correction plane, again starting the rotor up to operational speed; stopping the device and duly recording the vibrational values observed. During these runs, the position of the rotational indicia as frozen in position by the strobe is observed and this estimated information is written down. The operator then carries out a relatively involved series of mathematical tasks including a graphic determination of vectors. Correctional weights and orientations with respect to the reference indicia then are determined, the rotor is adjusted accordingly and, hopefully, balance within acceptable specifications is achieved. As is usually the case, this balancing is carried out in at least two planes which involves a further repetition of most of the above steps. In the past, where corrective balance remained inadequate, then the procedures as described above would be fully repeated, resulting in further extended down times and labor costs. In effect, there was no "trim" capability with the use of vibration analyzers in the field for balancing purposes. Such trim practices permit the additional correction for balance without the repetition of calibrating runs and the like. The technique involved has been in use for a considerable period of time. In this regard, the reader's attention is directed to a publication entitled "Dynamic Balancing of Rotating Machinery in the Field" by E. H. Thearle, Transactions of the American Society of Mechanical Engineers, October, 1934, No. 743.
Some improvement in the rapidity and accuracy of calculation has been achieved through the introduction of programmable portable calculating devices. With such devices, the mental and graphical mathematical steps are carried out automatically, however, the insertion of data still remains a manual task and, importantly, the visual observation of displacement of a reference mark utilizing the strobe represents a technique highly susceptible to error.
For any of the field balancing techniques qualified personnel are required, and the typical problems of human error persist. Because a number of steps are required to carry out balancing, particularly where additional trim balancing procedures are encountered, error readily may enter into the proper sequencing procedure itself to substantially negate the operator's efforts. Further, the entire sequential procedure of analysis must be repeated for each machine upon every return of the operator to the field. This necessarily entails the expenditure of considerable time with the consequent elevation of maintenance costs.